Steering device having a chain operated steering gear actuator

ABSTRACT

A power steering device according to this disclosure has first and second pairs of chain sprockets that are drivingly interconnected by a pair of roller chains. One pair of the sprockets is connected to a steering wheel by a steering shaft. The other pair of sprockets is drivingly connected to the pinion of a rack and pinion steering gear. A resiliently mounted chain tensioning device engages the portions of the chains that span the space between the two pairs of sprockets. The chain tensioner is displaced laterally when torque is transmitted through the chains from one set of sprockets to the other. A power steering valve senses the lateral displacement of the chain tensioner and functions to direct pressure fluid to one side or the other of a power steering booster cylinder in response to the movement of the tensioner.

United States Patent r1 1 Allison STEERING, DEVICE HAVING A CHAIN OPERATED STEERING GEAR ACTUATOR Inventor: William D. Allison, Grosse Pointe Farms, Mich.

Related US. Application Data Division of-Ser. No. 347,962, April 4, 1973.

U.S.'Cl 280/93, 74/242.8, 74/496 I'nt'. B62d 3/02 Field of Search 280/93, 96; 74/496, 498,

[56} References Cited UNlTED STATES PATENTS 6/1917 Parrett 280/96 11/1958 Mercier et a1. 180/792. R 12/1960 Blakstad 74/242.8

Mar. 4, 1975 [57] ABSTRACT A power steering device according to this disclosure has first and second pairs of chain sprockets that are drivingly interconnected by a pair of roller chains. One pair of the sprockets is connected to a steering wheel by a steering shaft. The other pair of sprockets is drivingly connected to the pinion of a rack and pinion steering gear. A resiliently mounted chain tensioning device engages the portions of the chains that span the space between the two pairs of sprockets. The chain tensioner is displaced laterally when torque is transmitted through the chains from one set of sprockets to the other. A power steering valve senses the lateral displacement of the chain tensioner and functions to direct pressure fluid to one side or the other of a power steering booster cylinder in response to the movement of the tensioner.

4 Claims, 5 Drawing Figures STEERING DEVICE, HAVING. A CHAIN OPERATED STEERING GEAR ACTUATOR This is a divisionof application Ser. No. 347,962,

. filed Apr. 4,1973.

SUMMARY OF THE DISCLOSURE ln'acco'rdance with the presentlypreferred embodiment of this invention, firstand secojnd pairs of chain sprocket-s are interconnected by a pair of roller chains. One pair of sprocketsis driven by a steering shaft which has a conventional steering wheel at its rearward end. The other pair of sprockets has a pinion drivingly connected to it. The pinion engages the rack of a rack and pinion steering gear.

A spring pressed levermechanism engages the portions of the roller chains that span the gap between the two pairs of sprockets. This mechanism operates as a chain tensioner. When torque is transmitted from one pair of sprockets to the other pair through the roller chain, the chain tensioner responds to tensile load in the chains and is displaced laterally thereby.

A power steering valve is connected to the chain tensioner so that when it is displaced laterally in response to the transmission of torque, the valve element of the steering valve is displaced accordingly. Displacement of the power steering valve element directs pressure BRIEF DESCRIPTION OF THE DRAWINGS The many objects and advantages of a power steering device constructed in accordance with this invention will become apparent upon consideration of the following detailed discussion and the accompanying drawings, in which:

FIG. 1 is a front elevational view of a power steering device for a motor vehicle with a portion of the device broken away to show the inner construction;

FIG. 2 is a side elevational view of the device of FIG.

FIG. 3 is a sectional view taken along section lines 3-3 of FIG. 1;

FIG. 4 is a sectional view taken along section lines 4-4 of FIG. I; and

FIG. Sis a sectional view of the power steering valve taken along section line 5-5 of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein the presently preferred embodiment of this invention is shown, FIG. 1 illustrates a power steering device 8 for a motor vehicle. The power steering device 8 includes a rack and pinion steering gear, a chain type steering gear actuator and a power steering valve responsive to chain displacement.

' The steering device 8 includes a metal housing 10 which 'rotatably supports a stub shaft 12-atits upper end. The shaft 12.is connected to a steering shaft as-.

sembly 14 which hasa steering wheel supported on its rearwardend. A pair of chain sprockets l6 and'l8 are fixed to the shaft 12.

A second shaft 20 isrotatably supported at the lower end of the housing 10 and has a pair of driven chain sprockets 22 and 24 connected thereto. Roller chain 26 vided as a contingency against the unlikely event there is an inadvertent mechanical failure of one of the chain drives.

A pinion 30 is mounted on the shaft 20. and is constructed to rotate with the driven sprockets 22 and 24. The pinion 30 engages the teeth of a rack 32. The rack 32 is urged into meshing engagement with the pinion '30 by spring pressed device 34. The rack 32 is con I nected in a conventional fashion to the steering linkage 36 of a motor vehicle steering system.

In accordance with the present invention, a resiliently mounted tensioning device engages the portions of the roller chains 26, 28 which extends between the two pairs of sprockets I6, 18 and 22,- 24. The chain tensioner includes a pair of upstanding links 40 and 42 which have their lower ends pivotally connected by pivot bolts 44 and and 46, respectively, to the, housing 10. In FIG. 1, the link '42 is not shown in order to reveal the other elements of the chain tensioner.

The links 40 and 42 extend upwardly from their pivot pins 44 and 46. A pair of generally lL-shape lever members 48 and50 are pivotally supported by the links 40 and 42. The L-shape member 48 is connected to the link 40 by a pivot pin 52. The upper end of the upstanding link 42 is pivotally connected to the L-shape member 50 by a pivot pin 54. A rigid cross link 56 interconnects the pivot pins 52 and 54.

The housing 10, the'upstanding links 40 and 42, and the cross link 56 form a parallelogram linkage system for the support of the L-shape members 48 and 50.

L-sliape member 48 has an' arcuate bearing surface 58 that faces inwardly and engages the chains 26 and 28. The bearing surface 58 is supported by a depending arm portion of the member 48. The member 48 also has an arcuate bearing surface 60 that faces outwardly and engages the chains 26 and 28.

L-shape member 50 has a depending arm 62 with a bearing portion 64 of arcuate shape that faces inwardly and'engages portions of the chains 26 and 28 that span the two sets of sprockets. An arcuate bearing portion 66 on the member 50 faces outwardly and engages the chains 26 and 28.

The L-s-hape members 48 and 50 have inwardly directed arms 68 and 70 which overlap. An intermediate member 72 has a cross pin 74 that engages aligned notches in the arm portions 68 and 70 of the members 48 and 50. The intermediate member 72 is urged upwardly by a coil spring 76 that is interposed between a shoulder formed on the intermediate member 72 and a support bracket portion 77 of the housing 10. The spring 76 urges the cross pin 74 carried by the intermediate member 72 upwardly into engagement with the arms 68 and 70 whereby the members 48 and 50 are urged in counterclockwise and clockwise rotation, respectively, (as viewed in FIG. 1).

The spring force on the L-shape members 48 and 50 causes their respective bearing members 58, 60 and 64, 66 to engage the chains 26 and 28. The portions of the chains 26, 28 that expand between the two pairs of sprockets assume an ogee configuration under the force of the spring 76 on the members 48, 50.

When torque is transmitted from one pair of sprockets to the otherpair of sprockets through the chains 26 and 28, the ogee shape portion of the chains carrying the tensile load will tend to'straighten. The straightening of the chain will cause the L-shape members 48 and 50 to pivot against the force of the spring 76. Because the members 48 and 50-are supported by articulated links 40, 42 and cross link 56, the entire linkage mechanismof the chain tensioner will be shifted laterally when the chains are loaded.

In accordance with the present invention, a power steering valve is provided which senses lateral displacement of the linkage type chain tensioner. A power steering valve 78 is mounted on the housing 10 in a position between the upstanding links 40 and 42. The power steering valve 78 is of the open center type and has a laterally shiftable spool type valve element 81 disposed within a central bore 80. The spool valve element 81 has a pair of end lands 82 and 84 and a central land 86.

The body of the valve 78 has a pressure inlet port 88 that is constructed to be connected to the outlet of a power steering pump. A return port 90 is arranged to be connected to the fluid return or sump of the power steering pump. The inlet port 88 communicates with an annular groove formed on the wall of the bore 80. The lands 84 and,86 are normally disposed on either side of the groove of port 88. A return port 90 communicates with a groove formed in the bore 80 that is normally situated between the valve lands 82 and 86.

A first outlet port 92 connects to-a centrally situated annular groove in the wall of bore 80. A second outlet port 94 is connected by a first passage with a groove in the bore 80 that is normally in alignment with thevalve land 84. Aninternal passage 95 provides communication between the second outlet port 94 and a groove in the bore 80-that is in alignmentwith the valve land 82.

Under normal straight-ahead drive conditions the components. will assume the orientation shown in FIG. 5.. With the inlet port 88 connected to a power steering pump, pressure fluid will enter the port 88, flow'axially past the periphery of the valve land 86 and out the return port 90. There will be no pressure buildup at the first and second outlet ports 92 and 94.

In the event the spool valve element 81 is shifted to the right, the valve land 86 will be displaced into sealed engagement with the bore, 80 closing the direct passage of pressure fluid to the return port 90. Fluid will flow from inlet port 88 through the second outlet port 94 to one side of a power steering booster cylinder (not shown). Under these circumstances, the displacement of the spool valve 81 will provide communication between the first outlet port 92 and the return port 90.

In the eventthe spool 81 is shifted to the left, direct communicationbetween the pressure inlet port 88 and the return port 90 will again be sealed by the central valve land 86. The second outlet port 94 will be closed and fluid will flow from the inlet port 88 to the first outlet port 92 and to the other side of the power steering booster cylinder. With the spool valve element 81 shifted to the left, second outlet port 94 will be in communication with the return port 90. v

In accordance with the present invention, means are provided to sense the transmission of torque from one pair of sprockets to the other pair of sprockets and to actuate the power. steering valve 78 in accordance therewith.

The power steering valve 78 is mounted in the housing 10 between the upstanding levers 40 and 42. The spool valve element has end portions 97 and 99 which protrude through seals 96 and 98 situated at the ends of the bore 80. The levers 40 and 42 have adjustment screws 100 and 102 with inner ends that are in engagement with the exposed ends 97 and 99 of the spool valve 81. As previously explained when torque is transmitted from the sprockets 16, 18 to the sprockets 22, 24 by rotation of the steering shaft 14, the ogee portions of the chains 26 and 28 that are under a tensile load will'straighten in opposition to the bias imposed thereon by the spring pressed L-shape members 48 and 50. The straightening of the chains under load will cause the members 48 and 50 to rotate and the entire linkage assembly to shift laterally a small amount. The displacement of the upstanding links 40 and 42 will be sensed by the spool valve element 81 which will: be shifted a corresponding amount. The displacement of the spool valve 81 will direct power steering fluid to the appropriate side of the power steeringbooster cylinder. .Thepower cylinder engages the rack 32 and is constructed to provide a boost or power assist to the operation of the rack and pinion steering gear.

- A power steering device, in accordance with this invention, provides a chain operated steering gear actuator having a resiliently mounted tension sensing means to actuate a power steering valve. The construction is particularly characterized by its simplicity and economy of manufacture. The majority of the components of the assembly can be manufactured from stamped sheet metal. v

The foregoing description presents the presently preferred embodiment of this invention. Modifications and alterations may occur to those skilled in the art which will'come within the sdope and spirit of the following claims. 3

I claim: I

1. A steering device for a motor vehicle including a steering gear actuator, i

said steering gear actuator having an input sprocket constructed to be connected to a vehicle steering wheel,

said actuator having an output sprocket constructed to be connected to a steering gear;

a drive chain drivingly interconnecting said input and output sprockets,

a chain tensionei' having a linkage system,

a pair of generally L-shape members supported by said linkage system,

spring means coupled to said members and urging each of said members into engagement with said chain at a pair of spaced locations.

said spring urged members biasing portions of said chain into generally ogee configurations 2. A steering device for a motor vehicle according to claim 1 and including:

H said linkage systemiof. said chain'ktensioner compris claim 1 and including:

ing links. arranged. n parallelogram. o a said chain tensioner having a parallelogram type link- 3. A steering devicefor a motor vehicle according to age System Supporting Said Irshape members claim 1 and including:

said pair of L-shape members having inwardly di- 5 meted Overlapping arms,

rected overlapping arms, I

said spring means engaging said overlapping arms Sal sprmfg means engagmg Sal over appmg arms and urging one of said members in a counterclock and urging one of sald members in a counterclockwise direction and the other f Said members in a wise direction and the other'of said members in a I clockwise direction. 0 clockwise direction.

4.VA steering device for-a motor vehicle according to said pair of Lshape members having inwardly di- 

1. A steering device for a motor vehicle including a steering gear actuator, said steering gear actuator having an input sprocket constructed to be connected to a vehicle steering wheel, said actuator having an output sprocket constructed to be connected to a steering gear; a drive chain drivingly interconnecting said input and output sprockets, a chain tensioner having a linkage system, a pair of generally L-shape members supported by said linkage system, spring means coupled to said members and urging each of said members into engagement with said chain at a pair of spaced locations, said spring urged members biasing portions of said chain into generally ogee configurations.
 2. A steering device for a motor vehicle according to claim 1 and including: said linkage system of said chain tensioner comprising links arranged in parallelogram form.
 3. A steering device for a motor vehicle according to claim 1 and including: said pair of L-shape members having inwardly directed overlapping arms, said spring means engaging said overlapping arms and urging one of said members in a counterclockwise direction and the other of said members in a clockwise direction.
 4. A steering device for a motor vehicle according to claim 1 and including: said chain tensioner having a parallelogram type linkage system supporting said L-shape members, said pair of L-shape members having inwardly directed overlapping arms, said spring means engaging said overlapping arms and urging one of said members in a counterclockwise direction and the other of said members in a clockwise direction. 